Abstract
Visually attended objects are afforded an enhancement of information relative to unattended objects, known as object-based attention (OBA). We recently demonstrated that shifts of OBA are anisotropic (what we call a Shift Direction Anisotropy, SDA), suggesting they are more efficient along the horizontal meridian compared to the vertical meridian (Barnas & Greenberg, 2016). Our goal here was to determine whether the SDA is driven by a specific shift direction (i.e., left-to-right or top-to-bottom) beyond a general horizontal shift advantage, and whether the SDA varies with visual field quadrant. Participants were presented with an L-shaped object, composed of a horizontal rectangle fused with a vertical rectangle. Following a partially valid peripheral cue, participants detected a target that appeared at the cued location ('valid') or at one of two equidistant, noncued locations at either the horizontal ('invalid-horizontal') or vertical ('invalid-vertical') object end. Results revealed no significant RT difference along the horizontal meridian when reallocating OBA left-to-right vs. right-to-left. However, there was a significant difference along the vertical meridian – RTs were significantly faster when reallocating OBA bottom-to-top vs. top-to-bottom. Additionally, horizontal shift advantages (invalid-horizontal RT < invalid-vertical RT) emerged in upper visual field quadrants, whereas vertical shift advantages (invalid-vertical RT < invalid-horizontal RT) emerged in lower visual field quadrants. These results suggest that the SDA emerges due to a specific impairment when shifting from top-to-bottom, as well as a general horizontal shift advantage, and is modulated by visual field quadrant. Together, these findings provide provisional support for a neurobiological explanation of the SDA based on the representation of the visual fields in retinotopically-mapped visual cortex.
Meeting abstract presented at VSS 2018